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FirefoxWeb browser · Mozilla

CVE-2016-1962

CRITICAL · 9.8 CVSS v3.0 Published 2016-03-13
Fix available
A fix is available. Upgrade to after 44.0.2 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Use-after-free vulnerability in the mozilla::DataChannelConnection::Close function in Mozilla Firefox before 45.0 and Firefox ESR 38.x before 38.7 allows remote attackers to execute arbitrary code by leveraging mishandling of WebRTC data-channel connections.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Use-after-free vulnerability in the mozilla::DataChannelConnection::Close function allows remote attackers to execute arbitrary code through mishandled WebRTC data-channel connections. The memory corruption occurs when the Close function is called on connections that have already been freed, enabling potential code execution.

MitigationUpgrade Mozilla Firefox to version 45.0 or later, or Firefox ESR to version 38.7 or later. Alternatively, disable WebRTC in browser settings if upgrade is not immediately feasible.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FirefoxWeb browser
Affected:<= 44.0.2= 38.0= 38.0.1= 38.0.5= 38.1.0= 38.1.1= 38.2.0= 38.2.1= 38.3.0= 38.4.0= 38.5.0= 38.5.1
LinuxOperating system
Affected:= 5.0= 6= 7
OpensuseOperating system
Affected:= 13.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Firefox version
    In Firefox, go to Help > About Firefox, or navigate to about:support. Alternatively, run 'firefox --version' from command line. On Oracle Linux/OpenSUSE, also check installed packages with 'rpm -q firefox' or 'zypper se firefox'
    Affected if Version matches <= 44.0.2 or any of: 38.0, 38.0.1, 38.0.5, 38.1.0, 38.1.1, 38.2.0, 38.2.1, 38.3.0, 38.4.0, 38.5.0, 38.5.1
  2. Confirm WebRTC is enabled
    In Firefox, type about:config in the address bar, then search for 'media.peerconnection.enabled'. Check if the value is set to true (enabled)
    Affected if media.peerconnection.enabled is set to true, meaning WebRTC is active in the browser
  3. Check for WebRTC add-ons or extensions
    Review installed add-ons in Firefox (Tools > Add-ons > Extensions) for any WebRTC-related extensions that may manipulate peer connection behavior
    Affected if WebRTC-manipulating extensions are installed alongside an affected Firefox version

User is affected if running an affected Firefox version (38.x series or <= 44.0.2) with WebRTC (media.peerconnection.enabled) enabled in the browser settings.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 44.0.2
Interim mitigation

Upgrade Mozilla Firefox to version 45.0 or later, or Firefox ESR to version 38.7 or later. Alternatively, disable WebRTC in browser settings if upgrade is not immediately feasible.

Recommended fix High confidence

Firefox 45.0 or later; Firefox ESR 38.7 or later

  1. 1. Check current Firefox version by navigating to Help > About Firefox or running 'firefox --version' in terminal
  2. 2. Download Firefox 45.0 or later (or Firefox ESR 38.7 or later for enterprise environments) from the official Mozilla website at https://www.mozilla.org/
  3. 3. Close all Firefox instances
  4. 4. Install the downloaded Firefox version using your system's package manager or the installer
  5. 5. Restart Firefox and verify the version has been updated to 45.0 or later (or 38.7+ for ESR) by checking Help > About Firefox
Caveat Firefox 45.0 includes significant changes; some legacy add-ons may be incompatible. Firefox ESR 38.7 is the recommended path for organizations needing stability.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-1962 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data